under one's arm; in the armpit
Refers to the area under the arm, often used when carrying something tucked there.
彼は小脇に本を抱えていた。
He was holding a book under his arm.
Standard kanji spelling.
Mixed kanji-kana spelling; less common but still seen.
Compound of 小 (ko, 'small') and 脇 (waki, 'side; armpit').